1. Field of the Invention
The present invention relates to a circuit substrate and a method of manufacturing the same and, in particular, to a circuit substrate including a rigid region and a flexible region and a method of manufacturing the same.
2. Description of the Related Art
One known example of a traditional circuit substrate is a wiring substrate described in Japanese Unexamined Patent Application Publication No. 2006-339186. The wiring substrate described in Japanese Unexamined Patent Application Publication No. 2006-339186 includes a flexible section and a rigid section disposed to be contiguous to the flexible section. The flexible section includes a flexible substrate in which wiring patterns are stacked such that an insulative resin layer is disposed therebetween. The rigid section includes a flexible substrate formed integrally with the flexible section. The wiring density of the wiring patterns in the rigid section is higher than that in the flexible section. Thus, the rigid section has a higher hardness than that of the flexible section.
However, for the wiring substrate described in Japanese Unexamined Patent Application Publication No. 2006-339186, the stray capacitance may increase, and the circuit characteristics may deviate from a desired value. More specifically, for the wiring substrate described in Japanese Unexamined Patent Application Publication No. 2006-339186, to have a higher wiring density of the wiring patterns in the rigid section than that in the flexible section, a redundant wiring pattern is disposed in the rigid section. The redundant wiring pattern faces other wiring patterns and forms unnecessary stray capacitance. As a result, the circuit characteristics in the wiring substrate described in Japanese Unexamined Patent Application Publication No. 2006-339186 deviate from a desired value.